Fix up new margins on modals by not setting auto until screen-sm-min. Fixes 11351: Correct grid class reset on input groups by using attribute selector, not an old class from v3 betas

BS3 commits: a52e528d2771e0f150682532b06c0f29fa6b0ad6,
853b69f2dfe66a839efa6216e9e7c1a530f92f62